Using the temperature-jump relaxation technique and other rapid and slow kinetic methods we shall investigate the followng properties of membranes: The time dependence or kinetic properties of membrane self-assembly; lipid phase separation and phase transition; vesicle fusion; and membrane permeation. In our laboratory we have recently been able to separate these different relaxation processes following a rapid temperature-jump of membrane suspensions. Specifically the following questions will be pursued. 1) What are the mechanisms, thermodynamic and kinetic parameters of membrane self-assembly, lipid phase transitions and phase separations, vesicle fusion and molecular transport? What is the effect of cholesterol and cholesterol esters? 2) Do lattice defects or pores exist in phospholipid bilayers and in natural membrane? If they do occur what role do they play in membrane phase transitions, protein-lipid interactions and cellular transport processes? 3) Human erythrocytes from different sources, such as normal vs. malignant cells or sickle cells, will be used to see whether the relaxation technique can be developed to detect minor alterations in the membrane structure and hence be useful as a clinical diagnostic tool. Information on kinetic and physical-chemical properties of lipid-aqueous systems will contribute to our understanding of membrane functions and lipid deposition diseases such as atherosclerosis. BIBLIOGRAPHIC REFERENCES: Tsong, T.Y., Effect of Phase Transition on the Kinetics of Dye Transport in Phospholipid Bilayer Structures, Biochemistry, 14, 5409 (1975). Tsong, T.Y., Transport of 8-Anilino-1-naphthalenesulfonate as a Probe of the Effect of Cholesterol on the Phospholipid Bilayer Structures, Biochemistry, 14, 5415 (1975).